Interpretation of Electric Field Gradients at Deuterium as Measured by Solid-State NMR Spectroscopy

Abstract

A simple interpretative scheme is presented to describe the deuterium quadrupole coupling constant and asymmetry parameter in a wide variety of chemical environments.

Active Sites in a Heterogeneous Organometallic Catalyst for the Polymerization of Ethylene

“…Terminal M–D are expected to have η = 0, bridging M–D–M that deviate from linearity is expected to have η ≠ 0, and C Q is expected to increase as the effective nuclear charge increases. 31 Thus, 2 H MAS NMR is capable of distinguishing between a variety of possible Zr–D structures in 4 - d 2 /Al i Bu 3 /Al 2 O 3 . …”

“…The line shape of a 2 H MAS NMR spectrum at the slow exchange limit is described by the quadrupolar coupling constant ( C Q , eq ) and the asymmetry parameter (η, eq ). Terminal M–D are expected to have η = 0, bridging M–D–M that deviate from linearity is expected to have η ≠ 0, and C Q is expected to increase as the effective nuclear charge increases . Thus, 2 H MAS NMR is capable of distinguishing between a variety of possible Zr–D structures in 4 - d 2 /Al i Bu 3 /Al 2 O 3 . …”

“…Terminal M−D are expected to have η = 0, bridging M−D−M that deviate from linearity is expected to have η ≠ 0, and C Q is expected to increase as the effective nuclear charge increases. 31 Thus, 2 (2) 39−41 In many cases, displacement of the bridging hydride by ethylene is slow relative to chain growth in olefin polymerization reactions in solution. 42−45 DFT studies of [Cp 2 ZrMe][MeAlO x ], formed from the reaction of Cp 2 ZrMe 2 with fully dehydroxylated alumina, showed that the metallocenium fragment is more weakly coordinated to certain sites on the alumina surface than a typical [MeB(C 6 F 5 ) 3 ] weakly coordinating anion.…”

Direct NMR Evidence for the Presence of Mobile Surface Hydrides on Ruthenium Nanoparticles

“…[16] By contrast, the HD molecule exhibits an intrinsic value of 227 kHz. [17] In order to characterise further the RuÀD bonding situation in nanoparticles and to determine whether the value of 63 kHz for the Ru-D component corresponds to the rigid limit, we plan additional 2 H NMR measurements of model complexes at different temperatures.…”

Coupled Methyl Group Rotation in FMN Radicals Revealed by Selective Deuterium Labeling

“…Up to now, most experimental values had been obtained from NMR and quadrupole spectroscopy of diamagnetic molecules. 2 H nqcs in spatially rigid C– 2 H bonds show a dependence on the hybridization of the carbon nucleus: for sp 3 sites, nqcs ∼170–175 kHz, for sp 2 sites 180–185 kHz, and for sp sites greater than 200 kHz have been reported. − Molecular motion or, more precisely, movement of the C– 2 H bond with respect to the external magnetic field will cause a reduction of these values. The fast rotation of methyl groups (around the pseudo-threefold spinning axis) in organic solids at elevated temperatures results in nqcs in the 45–55 kHz range with an anisotropy factor close to zero. , Therefore, we expect no sizable nqc in ENDOR resonances from the two methyl groups.…”